1. Field of the Invention
The present invention relates to an apparatus for analyzing blood in a non-invasive manner and a method using the same, and more particularly to an apparatus for analyzing blood components necessary for a hematology test by optically measuring blood flowing through blood vessels in a living body and a method using the same apparatus.
2. Description of the Related Art
The items of hematology tests such as the number of blood cells, hematocrit, hemoglobin, and corpuscular constant (mean corpuscular volume: MCV, mean corpuscular hemoglobin: MCH, and mean corpuscular hemoglobin concentration: MCHC) are extremely important for the diagnosis of diseases and the treatment thereof. Such items are most frequently used in clinical tests of patients.
Such a hematology test involves collecting blood from a living body to analyze the sample thereof with an analyzer. However, the collection of blood from the living body causes considerable pain to the living body. The above method for hematology tests is always accompanied by a fear that needles for blood collection might cause an accident due to erroneous injection when they are used for collecting blood from a different living body contracted with infectious diseases such as hepatitis and AIDS. Thus, a demand has been made for many years that an apparatus be developed that allows practitioners to perform a blood test in a non-invasive manner. When such a blood analyzer is installed beside the bed on which the living body is laid, the practitioners can monitor real-time conditions thereof on the spot without difficulty. Examples of the widely known prior art relating to such apparatus include a video microscope which applies light to a subject portion of observation on a skin surface of a living body to capture a video image thereof (static image) at a shutter speed of about one thousandth of a second and identifies discontinuous points in the blood stream which points move one by one on the static image, and an analyzer providing a video camera equipped with a high-speed shutter which captures red blood cells in the conjunctival capillary blood vessels in an eyeball (see Japanese Unexamined Patent Publication No. HEI 4-161915 published Jun. 5, 1992 and U.S. Pat. No. 4,998,533 issued to James W. Winkleman, Mar. 12, 1991).
By the way, the speed of blood flow is about five mm to ten mm per second. When images of red blood cells are captured at a shutter speed of one thousandth of a second like in the prior art, assuming that the blood flows at a rate of 10 mm per second, red blood cells move by the distance equal to the diameter thereof thereby generating a shift in the image by that diameter for consecutive shutter actuations.
Furthermore, red blood cells adjoin each other in blood vessels with a space of the diameter or less therebetween and almost all the red blood cells overlap each other in the image due to the shift in the image thereof. Consequently, the above Japanese prior art is far from allowing examiners to quantitatively measure the above test items through the morphological analysis of blood cells and the counting of the number thereof from captured images.
On the other hand, the analyzer disclosed in U.S. Pat. No. 4,998,533 captures conjunctival capillary blood vessels in an eyeball with the video camera. However, the focus of the video camera is relatively shifted at all times with respect to the captured portion of the eyeball because of a slight motion inherent in the eyeball. Thus, it is very difficult to repetitively capture the same region of the captured portion thereof with the video camera. It is impossible to mechanically stop the slight motion of the eyeball by closely contacting some object to eyeballs because the eyeball might be damaged. Furthermore, U.S. Pat. No. 4,998,533 describes counting the number of RBC and measuring HCT, MCV and MCHC, but it describes no procedure for measuring these values.